1. Field of the Invention
The present invention relates to a protocol conversion apparatus for converting a protocol of a data packet transferred between two apparatuses, for example, a personal computer and a portable telephone, which are provided with mutually different communication forms in protocol, in a case where the portable telephone is connected to the personal computer to have a communication with the exterior, said protocol conversion apparatus being interposed between said two apparatuses; a communication apparatus for performing a communication with the exterior, said communication apparatus being suitable for said protocol conversion apparatus; a communication program storage medium storing a communication program to operate the computer as the communication apparatus; a communication system having a function of performing a communication with the exterior while performing a protocol conversion; and a communication apparatus for performing a communication with the exterior, said communication apparatus having a function of the protocol conversion apparatus.
2. Description of the Related Art
Hitherto, there is well known a system for performing a communication between apparatuses. In such a system, in the event that those apparatuses have communication forms which are mutually different in protocol, it happens that a protocol conversion apparatus is interposed between those apparatuses. Now, let us consider, for example, a case where a communication is performed between a personal computer and a portable telephone. A communication according to radio is performed between the portable telephone and the third apparatus other than the personal computer. Here, let us consider a case where data is transmitted from the personal computer to the portable telephone, or data is transmitted from the portable telephone, which receives data from the exterior, to the personal computer.
In the portable telephone, a communication is performed in accordance with a communication protocol of PDC (Personal Digital Cellular) scheme by way of example. On the other hand, in the personal computer, a communication is performed in accordance with a communication protocol of USB (Universal Serial Bus) scheme by way of example. Thus, there is a need to dispose a protocol conversion apparatus between the personal computer and the portable telephone. The protocol conversion apparatus serves, in the that the personal computer is connected to the portable telephone to establish a communication system so that a radio communication is performed from the communication system to the exterior (the third apparatus), or data transmitted from the exterior on a radio basis is received, to convert a data packet having a data format based on a communication protocol of PDC scheme, which is obtained through reception by the portable telephone, into a data packet having a data format based on a communication protocol of USB scheme, which is capable of being dealt with by the personal computer, and also in the event that data generated or edited at the personal computer end is transmitted via the portable telephone to the exterior, to convert a data packet having the data format based on the communication protocol of USB scheme into the data packet having the data format based on the communication protocol of PDC scheme.
A data packet comprises user data, which is to be essentially transferred, and protocol data such as a header, a footer and the like, which is based on a communication protocol. In the protocol conversion apparatus, when the data packet based on a communication protocol of PDC scheme is transmitted from the portable telephone to the personal computer, the user data is picked up by means of removing the protocol data based on the communication protocol of PDC scheme, and a data packet based on the communication protocol of USB scheme is generated by means of applying the protocol data based on the communication protocol of USB scheme to the user data thus picked up, so that the data packet thus generated is transmitted to the personal computer.
On the other hand, in the protocol conversion apparatus, when the data packet based on a communication protocol of USB scheme is transmitted from the personal computer to the portable telephone, the user data is picked up by means of removing the protocol data based on the communication protocol of USB scheme, and a data packet based on the communication protocol of PDC scheme is generated by means of applying the protocol data based on the communication protocol of PDC scheme to the user data thus picked up, so that the data packet thus generated is transmitted to the portable telephone.
In this manner, a provision of the protocol conversion apparatus as mentioned above between two apparatuses wherein a communication is performed in accordance with individual communication protocols makes it possible to perform a communication between the apparatuses wherein a communication is performed in accordance with individual communication protocols.
Interposing the protocol conversion apparatus as mentioned above between two apparatuses makes it possible to perform a communication between even apparatuses wherein a communication is performed in accordance with mutually different communication protocols. However, according to the conventional protocol conversion apparatus, as mentioned above, the user data is picked up by means of removing the protocol data based on a communication protocol of one scheme from the data packet based on the one communication protocol, and a data packet based on the communication protocol of another scheme is generated by means of applying the protocol data based on the communication protocol of another scheme to the user data thus picked up. Such a conventional protocol conversion apparatus needs, however, a complicated processing. Usually, according to the conventional protocol conversion apparatus, there is a need to provide a hardware for performing a communication based on a communication protocol of one scheme, an additional hardware for performing a communication based on a communication protocol of another scheme, a CPU for converting the data packets received by those hardwares in a manner as described above, and a memory for storing a program to be executed by the CPU. This causes the apparatus to be complicated, and also the apparatus to be large-sized and to be expensive.